1, Reasons for bubble formation
The generation of bubbles during the silicone casting process mainly comes from the following aspects:
Raw material issue: Silicone raw materials may contain tiny air bubbles or impurities, which can expand or rupture during processing, forming visible bubbles.
Insufficient mixing and degassing: During the mixing process of silica gel, if the stirring is not uniform or the degassing is not sufficient, it will cause bubbles to be trapped in the material.
Unreasonable mold design: Improper or insufficient exhaust holes in the mold prevent gas from being discharged smoothly, resulting in the formation of bubbles during the silicone curing process.
Improper curing conditions: Improper control of curing temperature, time, and pressure may result in the formation of bubbles during the curing process of silicone gel.
Improper operation: In the process of silicone injection, demolding, etc., if the operation is improper, such as too fast injection speed, mold preheating, etc., it may also lead to the generation of bubbles.
2, Preventive measures and practical skills
To cast silicone that does not produce bubbles, we can start from the following aspects:
Optimize raw material selection: Choose high-quality silicone raw materials to ensure that they do not contain air bubbles and impurities. Meanwhile, according to specific application requirements, choose the appropriate type and hardness of silicone.
Thorough mixing and degassing: During the mixing process of silicone gel, it is important to ensure even stirring to remove as many bubbles as possible from the silicone gel. Vacuum degassing machine or manual stirring and tapping can be used to help bubbles escape from the silicone gel.
Reasonable design of molds: The design of molds should take into account the discharge of gases. Set sufficient exhaust holes on the mold and ensure that the position of the exhaust holes is reasonable, so that gas can be smoothly discharged. At the same time, the material and surface treatment of the mold should also meet the requirements of silicone casting to reduce the generation of bubbles.
Accurate control of curing conditions: curing temperature, time, and pressure are crucial for the curing process of silicone gel. These conditions should be precisely controlled according to the type and thickness of the silicone to ensure that the silicone can fully exhaust and cure evenly during the curing process.
Standardized operating procedures: In the processes of silicone infusion, demolding, etc., standardized operating procedures should be followed. The infusion speed should be moderate to avoid the generation of bubbles due to excessive speed; The mold should be preheated to an appropriate temperature before use to reduce the temperature difference between the silicone and the mold, thereby reducing the risk of bubble formation.
Use defoamer: In some cases, an appropriate amount of defoamer can be added to the silicone gel to help eliminate bubbles. However, it should be noted that the amount of defoamer used should be strictly controlled to avoid negative effects on the performance of silicone gel.
Post processing and inspection: After curing, silicone products should undergo necessary post-processing, such as trimming, polishing, etc., to further improve product quality. At the same time, the product should be inspected to ensure that there are no defects such as bubbles present.
3, Case analysis and practical experience
In practical operation, we can further understand how to cast silicone gel that does not produce bubbles through the following examples:
Case 1: A certain automotive parts manufacturer discovered a large number of bubbles on the surface of the product during the silicone casting process. After analysis, it was found that it was caused by the unreasonable design of the mold exhaust hole. Subsequently, they redesigned the exhaust holes of the mold and increased the number of exhaust holes. After improvement, the bubble problem of the product has been effectively solved.
Case 2: A medical device manufacturer found that the problem of bubbles was difficult to solve during the silicone casting process. They tried various methods, including optimizing raw materials and improving mixing processes, but the results were not satisfactory. In the end, they decided to add an appropriate amount of defoamer to the silicone gel and strictly control the amount of defoamer used. After practical verification, this method significantly reduces the generation rate of bubbles.
